This invention relates to hammer drivers for impact printers and, more particularly, to variable energy electromagnetic drivers for the hammers of such printers.
Hammer-type impact printing mechanisms are most commonly found in computer printers and the like where printing speed, rather than print quality, is the predominant concern. However, it is known that high quality (e.g., typewriter quality) printing may be carried out with such a printing mechanism, if the hammer impact energy is varied in manner tending to compensate for the tendency of different classes of characters to print with different densities.
Unfortunately, prior variable energy hammer drivers have not been altogether successful, primarily because of the difficulty which has been experienced in attempting to hold set point hammer impact energy levels for the different classes of characters, especially when high speed printing is called for. It is believed that one of the major causes of that shortcoming is that such a driver is normally subjected to repeated applications of shock forces, especially on the return or rebound strokes of the hammer.